(1) Field of the Invention
This invention is concerned with improvements relating to heat storage units.
In heat storage units it is practice to remove heat from the storage section by drawing air through an air inlet into the unit, by means of an impeller device of the unit, passing such air along a heating passage or passages extending through the heat storage section, and to deliver such air to the room being served by the unit through an air outlet.
It has been suggested that it would be convenient to be able to use the impeller device of the heat storage unit to draw air through the air inlet into the unit, and to deliver such air directly through the air outlet, without the air passing through the heating passages. In this manner the impeller device of the storage unit could be used to provide for circulation of air without causing heating of the air.
(2) Description of the Prior Art
A conventional heat storage unit comprises a valve chamber above which the heat storage section is mounted: the heating passages extend from one part of the chamber through the heat storage section, between the heat storage elements thereof, returning to a different part of the chamber. Thus, it has been suggested to provide valve means movable between a first condition (in which the heat storage unit may be said to be operating in its cool running condition) in which the flow of air from the air inlet to the air outlet is directly through the valve chamber, and a second condition (in which the storage unit may be said to be operating in its heating condition) in which such air flows from one part of the valve chamber to the other by way of the heating passage or passages.
In previous suggestions the valve means, when in its first condition, has been operative to close off the heating passages whilst permitting flow of air directly through the valve chamber. In one such previous suggestion, the valve means was operative to close off the heating passage at the point of its exit from the valve chamber, whilst in another previous suggestion, separate valve elements were provided which were operative to close off the heating passage both at the point of its exit from the valve chamber and at the point of its return to the valve chamber. Examples of such previous suggestions may be found in U.K. Patent Specification No. 1,254,691 and in German OLS No. 683,372.
In all previous suggestions, difficulty has been encountered in preventing air flow through the heating passages to the required extent, when operating the storage unit in the cool running condition. It has been discovered that this difficulty is primarily caused by the existence of a pressure differential between the two parts of the valve chamber from which the heating passages extend from and return to the valve chamber when the heat storage unit is operating in its cool running condition, together with the difficulty of providing a closing off of the heating passages to an extent sufficient to prevent significant flow of air under the influence of this pressure differential. Such difficulties are exacerbated (a) by the temperature at which it is necessary for the valve means to be effective, and (b) by the fact that, when in its fully charged condition, a very small flow of air through the heating passages can cause a significant dissipation of the heat stored in the heat sorage elements. Whereas such dissipation is not necessarily significant in relation to the rise in temperature which it creates whilst the storage unit is operating in its cool running condition, it may be significant in relation to the capability of the unit to retain sufficient store heat for the subsequent period when it is desired to utilise the unit in the maintenance of an optimum temperature in the room being served by the unit.
Thus, previous suggestions, to use the impeller device of the storage unit to provide for circulation of the air without causing heating of the air, have not been successful.